Field of the Invention
The present invention relates to a light emission control device including an accumulator unit, a method of controlling the same, and a storage medium, as well as an image pickup apparatus, and more particularly to charge/discharge control for a light emitting device used in an image pickup apparatus, such as a digital camera.
Description of the Related Art
In general, in a light emitting device (hereinafter referred to as the strobe device) used in an image pickup apparatus, such as a digital camera, a xenon tube is used as a light source (light emitting section). On the other hand, in the strobe device using the xenon tube, the xenon tube and a capacitor used for charge and discharge are large in volume. Further, to cause the xenon tube to emit light, it is necessary to generate high voltage of several kV as a trigger voltage. When taking this as well into consideration, it is difficult to achieve size reduction of the strobe device.
To solve this problem, there has been proposed a strobe device that uses, as a light source, a light emitting diode (LED) which is a high-luminance semiconductor light emitting device. The strobe device using the LED can be reduced in thickness and size by using an electric double layer capacitor (EDLC) having high volumetric efficiency.
Incidentally, in the strobe device, charge level control is performed by taking power efficiency and operability into account. For example, there has been proposed a strobe charge control method in which a main capacitor is charged with a large current up to a charge level at which the strobe device is capable of emitting light, and when the operation mode is changed to a photographing mode, the main capacitor is subjected to supplemental charging with a constant small current so as to make up for self-discharge (see Japanese Patent Laid-Open Publication No. 2000-358191).
Incidentally, in the strobe device using the electric double layer capacitor, if the strobe device is driven at a high voltage for a long time period, the lifetime of the electric double layer capacitor is reduced. In view of this, charge control is performed such that the charge voltage is increased to a voltage required to perform flash light emission only when performing photographing, and when the power is turned off, by taking the lifetime of the capacitor the voltage into consideration, the charge voltage is reduced to a predetermined voltage (predetermined level) or lower.
However, in a case where the electric double layer capacitor is discharged to the predetermined level whenever photographing is terminated, when repeatedly performing photographing, the charging time required to perform flash light emission becomes longer, which degrades the operability. Further, since the capacitor is discharged to the predetermined level, electric power which has been once charged is wasted. Furthermore, when the operability and the power efficiency of the image pickup apparatus (i.e. the strobe device) are considered, it is preferable not to proactively perform the discharge control for a time period during which there is a high possibility that the user performs photographing.
On the other hand, when the power is turned off, it is preferable to lower the voltage of the electric double layer capacitor to the predetermined level or lower by taking the durability of the electric double layer capacitor into consideration. However, if the voltage during operation is increased by taking the operability and the power efficiency into consideration, it takes a lot of time to complete discharge processing when the power is turned off, which results in an increase in time before the image pickup apparatus is shut down.